/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.MoreObjects;
import com.google.common.collect.Tables.AbstractCell;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Spliterator;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.stream.Collector;
import javax.annotation.Nullable;

/**
 * A {@link Table} whose contents will never change, with many other important
 * properties detailed at {@link ImmutableCollection}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained">
 * immutable collections</a>.
 *
 * @author Gregory Kick
 * @since 11.0
 */
@GwtCompatible
public abstract class ImmutableTable<R, C, V> extends AbstractTable<R, C, V>
    implements Serializable {

  /**
   * Returns a {@code Collector} that accumulates elements into an {@code ImmutableTable}. Each
   * input element is mapped to one cell in the returned table, with the rows, columns, and values
   * generated by applying the specified functions.
   *
   * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time
   * if the row, column, or value functions return null on any input.
   *
   * @since 21.0
   */
  @Beta
  public static <T, R, C, V> Collector<T, ?, ImmutableTable<R, C, V>> toImmutableTable(
      Function<? super T, ? extends R> rowFunction,
      Function<? super T, ? extends C> columnFunction,
      Function<? super T, ? extends V> valueFunction) {
    checkNotNull(rowFunction);
    checkNotNull(columnFunction);
    checkNotNull(valueFunction);
    return Collector.of(
        () -> new ImmutableTable.Builder<R, C, V>(),
        (builder, t) ->
            builder.put(rowFunction.apply(t), columnFunction.apply(t), valueFunction.apply(t)),
        (b1, b2) -> b1.combine(b2),
        b -> b.build());
  }

  /**
   * Returns a {@code Collector} that accumulates elements into an {@code ImmutableTable}. Each
   * input element is mapped to one cell in the returned table, with the rows, columns, and values
   * generated by applying the specified functions. If multiple inputs are mapped to the same row
   * and column pair, they will be combined with the specified merging function in encounter order.
   *
   * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time
   * if the row, column, value, or merging functions return null on any input.
   *
   * @since 21.0
   */
  public static <T, R, C, V> Collector<T, ?, ImmutableTable<R, C, V>> toImmutableTable(
      Function<? super T, ? extends R> rowFunction,
      Function<? super T, ? extends C> columnFunction,
      Function<? super T, ? extends V> valueFunction,
      BinaryOperator<V> mergeFunction) {

    checkNotNull(rowFunction);
    checkNotNull(columnFunction);
    checkNotNull(valueFunction);
    checkNotNull(mergeFunction);

    /*
     * No mutable Table exactly matches the insertion order behavior of ImmutableTable.Builder, but
     * the Builder can't efficiently support merging of duplicate values.  Getting around this
     * requires some work.
     */

    return Collector.of(
        () -> new CollectorState<R, C, V>()
            /* GWT isn't currently playing nicely with constructor references? */,
        (state, input) ->
            state.put(
                rowFunction.apply(input),
                columnFunction.apply(input),
                valueFunction.apply(input),
                mergeFunction),
        (s1, s2) -> s1.combine(s2, mergeFunction),
        state -> state.toTable());
  }

  private static final class CollectorState<R, C, V> {
    final List<MutableCell<R, C, V>> insertionOrder = new ArrayList<>();
    final Table<R, C, MutableCell<R, C, V>> table = HashBasedTable.create();

    void put(R row, C column, V value, BinaryOperator<V> merger) {
      MutableCell<R, C, V> oldCell = table.get(row, column);
      if (oldCell == null) {
        MutableCell<R, C, V> cell = new MutableCell<>(row, column, value);
        insertionOrder.add(cell);
        table.put(row, column, cell);
      } else {
        oldCell.merge(value, merger);
      }
    }

    CollectorState<R, C, V> combine(CollectorState<R, C, V> other, BinaryOperator<V> merger) {
      for (MutableCell<R, C, V> cell : other.insertionOrder) {
        put(cell.getRowKey(), cell.getColumnKey(), cell.getValue(), merger);
      }
      return this;
    }

    ImmutableTable<R, C, V> toTable() {
      return copyOf(insertionOrder);
    }
  }

  private static final class MutableCell<R, C, V> extends AbstractCell<R, C, V> {
    private final R row;
    private final C column;
    private V value;

    MutableCell(R row, C column, V value) {
      this.row = checkNotNull(row);
      this.column = checkNotNull(column);
      this.value = checkNotNull(value);
    }

    @Override
    public R getRowKey() {
      return row;
    }

    @Override
    public C getColumnKey() {
      return column;
    }

    @Override
    public V getValue() {
      return value;
    }

    void merge(V value, BinaryOperator<V> mergeFunction) {
      checkNotNull(value);
      this.value = checkNotNull(mergeFunction.apply(this.value, value));
    }
  }

  /** Returns an empty immutable table. */
  @SuppressWarnings("unchecked")
  public static <R, C, V> ImmutableTable<R, C, V> of() {
    return (ImmutableTable<R, C, V>) SparseImmutableTable.EMPTY;
  }

  /** Returns an immutable table containing a single cell. */
  public static <R, C, V> ImmutableTable<R, C, V> of(R rowKey, C columnKey, V value) {
    return new SingletonImmutableTable<R, C, V>(rowKey, columnKey, value);
  }

  /**
   * Returns an immutable copy of the provided table.
   *
   * <p>The {@link Table#cellSet()} iteration order of the provided table
   * determines the iteration ordering of all views in the returned table. Note
   * that some views of the original table and the copied table may have
   * different iteration orders. For more control over the ordering, create a
   * {@link Builder} and call {@link Builder#orderRowsBy},
   * {@link Builder#orderColumnsBy}, and {@link Builder#putAll}
   *
   * <p>Despite the method name, this method attempts to avoid actually copying
   * the data when it is safe to do so. The exact circumstances under which a
   * copy will or will not be performed are undocumented and subject to change.
   */
  public static <R, C, V> ImmutableTable<R, C, V> copyOf(
      Table<? extends R, ? extends C, ? extends V> table) {
    if (table instanceof ImmutableTable) {
      @SuppressWarnings("unchecked")
      ImmutableTable<R, C, V> parameterizedTable = (ImmutableTable<R, C, V>) table;
      return parameterizedTable;
    } else {
      return copyOf(table.cellSet());
    }
  }
  
  private static <R, C, V> ImmutableTable<R, C, V> copyOf(
      Iterable<? extends Cell<? extends R, ? extends C, ? extends V>> cells) {
    ImmutableTable.Builder<R, C, V> builder = ImmutableTable.builder();
    for (Cell<? extends R, ? extends C, ? extends V> cell : cells) {
      builder.put(cell);
    }
    return builder.build();
  }

  /**
   * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
   * Builder#Builder() ImmutableTable.Builder()} constructor.
   */
  public static <R, C, V> Builder<R, C, V> builder() {
    return new Builder<R, C, V>();
  }

  /**
   * Verifies that {@code rowKey}, {@code columnKey} and {@code value} are
   * non-null, and returns a new entry with those values.
   */
  static <R, C, V> Cell<R, C, V> cellOf(R rowKey, C columnKey, V value) {
    return Tables.immutableCell(checkNotNull(rowKey), checkNotNull(columnKey), checkNotNull(value));
  }

  /**
   * A builder for creating immutable table instances, especially {@code public
   * static final} tables ("constant tables"). Example: <pre>   {@code
   *
   *   static final ImmutableTable<Integer, Character, String> SPREADSHEET =
   *       new ImmutableTable.Builder<Integer, Character, String>()
   *           .put(1, 'A', "foo")
   *           .put(1, 'B', "bar")
   *           .put(2, 'A', "baz")
   *           .build();}</pre>
   *
   * <p>By default, the order in which cells are added to the builder determines
   * the iteration ordering of all views in the returned table, with {@link
   * #putAll} following the {@link Table#cellSet()} iteration order. However, if
   * {@link #orderRowsBy} or {@link #orderColumnsBy} is called, the views are
   * sorted by the supplied comparators.
   *
   * For empty or single-cell immutable tables, {@link #of()} and
   * {@link #of(Object, Object, Object)} are even more convenient.
   *
   * <p>Builder instances can be reused - it is safe to call {@link #build}
   * multiple times to build multiple tables in series. Each table is a superset
   * of the tables created before it.
   *
   * @since 11.0
   */
  public static final class Builder<R, C, V> {
    private final List<Cell<R, C, V>> cells = Lists.newArrayList();
    private Comparator<? super R> rowComparator;
    private Comparator<? super C> columnComparator;

    /**
     * Creates a new builder. The returned builder is equivalent to the builder
     * generated by {@link ImmutableTable#builder}.
     */
    public Builder() {}

    /**
     * Specifies the ordering of the generated table's rows.
     */
    @CanIgnoreReturnValue
    public Builder<R, C, V> orderRowsBy(Comparator<? super R> rowComparator) {
      this.rowComparator = checkNotNull(rowComparator);
      return this;
    }

    /**
     * Specifies the ordering of the generated table's columns.
     */
    @CanIgnoreReturnValue
    public Builder<R, C, V> orderColumnsBy(Comparator<? super C> columnComparator) {
      this.columnComparator = checkNotNull(columnComparator);
      return this;
    }

    /**
     * Associates the ({@code rowKey}, {@code columnKey}) pair with {@code
     * value} in the built table. Duplicate key pairs are not allowed and will
     * cause {@link #build} to fail.
     */
    @CanIgnoreReturnValue
    public Builder<R, C, V> put(R rowKey, C columnKey, V value) {
      cells.add(cellOf(rowKey, columnKey, value));
      return this;
    }

    /**
     * Adds the given {@code cell} to the table, making it immutable if
     * necessary. Duplicate key pairs are not allowed and will cause {@link
     * #build} to fail.
     */
    @CanIgnoreReturnValue
    public Builder<R, C, V> put(Cell<? extends R, ? extends C, ? extends V> cell) {
      if (cell instanceof Tables.ImmutableCell) {
        checkNotNull(cell.getRowKey());
        checkNotNull(cell.getColumnKey());
        checkNotNull(cell.getValue());
        @SuppressWarnings("unchecked") // all supported methods are covariant
        Cell<R, C, V> immutableCell = (Cell<R, C, V>) cell;
        cells.add(immutableCell);
      } else {
        put(cell.getRowKey(), cell.getColumnKey(), cell.getValue());
      }
      return this;
    }

    /**
     * Associates all of the given table's keys and values in the built table.
     * Duplicate row key column key pairs are not allowed, and will cause
     * {@link #build} to fail.
     *
     * @throws NullPointerException if any key or value in {@code table} is null
     */
    @CanIgnoreReturnValue
    public Builder<R, C, V> putAll(Table<? extends R, ? extends C, ? extends V> table) {
      for (Cell<? extends R, ? extends C, ? extends V> cell : table.cellSet()) {
        put(cell);
      }
      return this;
    }
    
    Builder<R, C, V> combine(Builder<R, C, V> other) {
      this.cells.addAll(other.cells);
      return this;
    }

    /**
     * Returns a newly-created immutable table.
     *
     * @throws IllegalArgumentException if duplicate key pairs were added
     */
    public ImmutableTable<R, C, V> build() {
      int size = cells.size();
      switch (size) {
        case 0:
          return of();
        case 1:
          return new SingletonImmutableTable<R, C, V>(Iterables.getOnlyElement(cells));
        default:
          return RegularImmutableTable.forCells(cells, rowComparator, columnComparator);
      }
    }
  }

  ImmutableTable() {}

  @Override
  public ImmutableSet<Cell<R, C, V>> cellSet() {
    return (ImmutableSet<Cell<R, C, V>>) super.cellSet();
  }

  @Override
  abstract ImmutableSet<Cell<R, C, V>> createCellSet();

  @Override
  final UnmodifiableIterator<Cell<R, C, V>> cellIterator() {
    throw new AssertionError("should never be called");
  }

  @Override
  final Spliterator<Cell<R, C, V>> cellSpliterator() {
    throw new AssertionError("should never be called");
  }

  @Override
  public ImmutableCollection<V> values() {
    return (ImmutableCollection<V>) super.values();
  }

  @Override
  abstract ImmutableCollection<V> createValues();

  @Override
  final Iterator<V> valuesIterator() {
    throw new AssertionError("should never be called");
  }

  /**
   * {@inheritDoc}
   *
   * @throws NullPointerException if {@code columnKey} is {@code null}
   */
  @Override
  public ImmutableMap<R, V> column(C columnKey) {
    checkNotNull(columnKey);
    return MoreObjects.firstNonNull(
        (ImmutableMap<R, V>) columnMap().get(columnKey), ImmutableMap.<R, V>of());
  }

  @Override
  public ImmutableSet<C> columnKeySet() {
    return columnMap().keySet();
  }

  /**
   * {@inheritDoc}
   *
   * <p>The value {@code Map<R, V>} instances in the returned map are
   * {@link ImmutableMap} instances as well.
   */
  @Override
  public abstract ImmutableMap<C, Map<R, V>> columnMap();

  /**
   * {@inheritDoc}
   *
   * @throws NullPointerException if {@code rowKey} is {@code null}
   */
  @Override
  public ImmutableMap<C, V> row(R rowKey) {
    checkNotNull(rowKey);
    return MoreObjects.firstNonNull(
        (ImmutableMap<C, V>) rowMap().get(rowKey), ImmutableMap.<C, V>of());
  }

  @Override
  public ImmutableSet<R> rowKeySet() {
    return rowMap().keySet();
  }

  /**
   * {@inheritDoc}
   *
   * <p>The value {@code Map<C, V>} instances in the returned map are
   * {@link ImmutableMap} instances as well.
   */
  @Override
  public abstract ImmutableMap<R, Map<C, V>> rowMap();

  @Override
  public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
    return get(rowKey, columnKey) != null;
  }

  @Override
  public boolean containsValue(@Nullable Object value) {
    return values().contains(value);
  }

  /**
   * Guaranteed to throw an exception and leave the table unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @Deprecated
  @Override
  public final void clear() {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the table unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @Override
  public final V put(R rowKey, C columnKey, V value) {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the table unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @Deprecated
  @Override
  public final void putAll(Table<? extends R, ? extends C, ? extends V> table) {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the table unmodified.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Unsupported operation.
   */
  @CanIgnoreReturnValue
  @Deprecated
  @Override
  public final V remove(Object rowKey, Object columnKey) {
    throw new UnsupportedOperationException();
  }

  /** Creates the common serialized form for this table. */
  abstract SerializedForm createSerializedForm();

  /**
   * Serialized type for all ImmutableTable instances. It captures the logical contents and
   * preserves iteration order of all views.
   */
  static final class SerializedForm implements Serializable {
    private final Object[] rowKeys;
    private final Object[] columnKeys;

    private final Object[] cellValues;
    private final int[] cellRowIndices;
    private final int[] cellColumnIndices;

    private SerializedForm(
        Object[] rowKeys,
        Object[] columnKeys,
        Object[] cellValues,
        int[] cellRowIndices,
        int[] cellColumnIndices) {
      this.rowKeys = rowKeys;
      this.columnKeys = columnKeys;
      this.cellValues = cellValues;
      this.cellRowIndices = cellRowIndices;
      this.cellColumnIndices = cellColumnIndices;
    }

    static SerializedForm create(
        ImmutableTable<?, ?, ?> table, int[] cellRowIndices, int[] cellColumnIndices) {
      return new SerializedForm(
          table.rowKeySet().toArray(),
          table.columnKeySet().toArray(),
          table.values().toArray(),
          cellRowIndices,
          cellColumnIndices);
    }

    Object readResolve() {
      if (cellValues.length == 0) {
        return of();
      }
      if (cellValues.length == 1) {
        return of(rowKeys[0], columnKeys[0], cellValues[0]);
      }
      ImmutableList.Builder<Cell<Object, Object, Object>> cellListBuilder =
          new ImmutableList.Builder<Cell<Object, Object, Object>>(cellValues.length);
      for (int i = 0; i < cellValues.length; i++) {
        cellListBuilder.add(
            cellOf(rowKeys[cellRowIndices[i]], columnKeys[cellColumnIndices[i]], cellValues[i]));
      }
      return RegularImmutableTable.forOrderedComponents(
          cellListBuilder.build(), ImmutableSet.copyOf(rowKeys), ImmutableSet.copyOf(columnKeys));
    }

    private static final long serialVersionUID = 0;
  }

  final Object writeReplace() {
    return createSerializedForm();
  }
}
